Machine telephone switching system.



F. R.. MCQERTY L D. KOENlG.

MACHINE ELEPHoNE swlcHmG SYSTEM.

AFFLXCATION FlLED MAR. 2. W14.

F. E, MCBER'Y L D. KOENlG.

umm-E ELEPHoNE swacame SYSTEM. A??LICATION FILED MAR. 2, 9l4.

Patented Nov. 16, 1915.

Hq. ff".

F. R. NieQi-:RTV e D. KGENS.

MACHINE TELEFHNE SWWCHWG SYSEeL APPLlcATioN FILED MAR. 2. 1914.

faeate Nov. M3, 19H).

9 SHEETS-SHEET 3.

MACHINE ELEPHONE SWITCrlG SYSTEM.

APPUCATION FRED MRZ, W14.

Ummm;

9 SHEETS-SHEET W/fnesses as y J F. R. MCBERTY & D. KOENiG. MACHINE THEPHONE swlTcHmG SYSTEM.

y APPLICATION FILED MAR.2. 1914.

F. E. MQBERTY & D, KOENiG.

mamme TELEPHONE swzTcHmG SYSTEM.

APPUEATION FILED HRVZ, l1914.

Patente Nov. 16, 1915.r

F. R. MCBERTY D. KOENIG. MACHINE TELEPHONE swwcmm sYsTsM.

l v l APPLICANON FILED MAR. 2, 1914 1,150,181-

APPLiCATION FILED MR. Z.

Mfr/eases:

F. n.' MCBERT'MQ D. Koma..- MACHINE TELEPHONE SWITCHING SYSTEM.

MAPPucATioN FILED MAH.; 1914. Y

Patented Now?. 16, 1915.

9 SHEETS-'SHEET 9.

onsu uw) SYStem this?. de

mms

hue

mired mm piace mj; take type previously known. the

only be niade that in .l 1 ig. the seipience sr'itcb contacts ot the vthree sequence switches shown thereon are associated with the sequence switch indicated iii that portion of the figure separated troni the remaining portions by dotted lines.

'.llie tiual selector switch ditllers troni the tinal select-or switches of this type previously known only by the addition et two extra notches in the interrupter plate of the top thereof, between the first 1t) notches thereof and the second 10 notches thereo't. lt will be recalled that selector switches' ot' this type have a capacita',7 of two hundred lines, and the. contacts ota these lines are arranged in ten levels of twenty lines each. yBetween the bank of the one. hundred lines inifiivirflual to one hundred, and the bariliv ot lines individual to another hundred, that is to say, between the tirst ten lines oi each level and the second ten lines of each level there is a spacing plate.. In selector switches of this spacing between the two banks of line contacts was without etlect, as the interruptor plate at the top of the selector was uncut over thev portion thereof .correspoinling to the spacingl plat ln the final selector switches as used here? in, however, there are two notches cut in the portion of the. nterrupter `plate corresponding to the sparing plate tor purposes herein described. That is to say, in selecting a line in the tiret set of ten liiies'on/a giron level, the interrupter will operate a number of tinies corresponding to the nuui- 32er of lines passed over, whereas, in seleeting a line in the second set oi" ten contant-s on suoli given level, the interrupter will operate a number of tinies corresponding to the. number ot lines passed over plus two. Thiswill be readilyv understood i'roni an examination of l? ig. 5 in which the notches a represent the notches of such interrupter plate. corresponding to the .rst set ot ten lines on the given level of the selector; the notches l) represent the notches in such plate corresponding to the second set of 'ten lines on such level, and the two notches c represent the two extra or additional notches.

which have been added as above indicated -or purposes 'hereinafter described.

The invention as disclosed herein will be best understood from a desrriptii'ui oit the operation ot the system shown.

ssuuiing that the subscriber at the substation indicated at 120 desires connection lwith the subscriber indicated at 320, whose nuniber is 307. he first removes his receiver from its switchliook, thereby closing a circuit for the line relay 121 which, on its energi'zationfcloses a circuit for and energizes the pilotrelay 122 common to a group of i coming lines which appear niultipled upon a given group of first line finders such as the one shown in F ig. 1. Relay 122 closes the line rela).y

therefore. start in niotion, inoving their' brushes 125, 126. 12T, 12S over the terminals 120. 130, 131, 132 ot" the lines appearing in such line finders, and testing such lines in the usual way. As one ot tliein, however, brings its brushes into contact with the terminals ot the walling line` it. will find upon the tei-initial 132 of such line a selectable i'ioten'tial produred b v the eiiergization of "2l and determined by the rcsistanees i233 and lill. linniediately that the brush 128 reines in contact with the terminal 132 upon which suoli selectable potential exist-s, the test rel-.iv 135 will be energized over the springs 102 bottoni, 108 top and either the spring 10o or the interruptor so reducing the potential. upon the terminal 132 that such potential is no longer selectable, and any other line finder \vliosebrusli 128 conies in Contact with such terminal 132 will not. be stopped. 'llie carriage of the line finder which has thus seized the line, continues in niotion, however, until its brushes are propf'ri)v centered upon the terminals of the calling line, at which time the circuit. through the interrupter brush 136 will be open, and the shunt being removed troni around the power control test relay 13?, such relai will be energized, opening the circuit ot the power magnet 123 and closing the circuit o in the holding magnet 13S over the springs 105 top and 107, tliere- 112 bottom, the spring 102 bottoni being opened as the sequence switch leaves its first position. in the second position the spring 110 being closed, the eut-off relay 139 of the calling' line is energized, causing the denergization ot' the line relay 121 and the consequent deiincrgizat-ion of the pilot rela)7 122. provided no other line of this group is at this time calling and not as yet been seized by a line finder. The denergization of the rela;r 121 opens the battery t" cuit to the terminals 132, and the line now haring been seized and heilig maintained busy. no selectable potential is pos sible upon its test terminal 132.

The sequence switch 100, on coming into released by the hanging up of the receiver of the calling subscriber, as will `be hereinafter described.

As the sequenceswitch 600 moved into its third position it closed the circuit'over the spring (309 to drive the sequence switch 200 also to its third position. ln this position springs 210 bottom and 211 bottom are closed, and the impulse receiving circuit from the subscriber-is substation to the reg- .first line iinder switch, -terminal 231 and brush'll' oi.I the second line finder switch,

spring` 211 bottom to ground and back` to battery.

rlhe relay 420 being energized, as before described the sequence. switch e100 is driven out ot 4its iirst and into its fourth position.

lt will be observed that the calling subscribei"s supervisory relay 241, which at this time controls restoration and whichin position 2 and positionl and positions subsequent thereto is directly under the control oi' the callinfoi` subscriber, energized bythe closure of a spring The apparatus will now await the sending;l ot impulses by the calling' subscriber, such impulses being` arranged in groups corre spondinn' to the complement of the digits of the numerical designation of the called sub-, scriber`s station-that is to say, the called subscribers number being' assumed to be 307, the calling subscriber will transmit to the canti-al station three series of impulses, the

-iirst series comprising' seven'impulses, the

second series comprisingT ten impulses, and the. third series comi'irisingr three impulses. ln each of these series of impulses Athe last impulse sent will be relatively longer than the other impulses ot the series, which other impulses are, in fact. quite short. The sender b v which these impulses are sent may be of any desired structural character, provided that the impulses are sent in a com' pleurent-ary manner. and that the last of each ot the groups ot rimpulses sent by such de vice'is relatively longer than the other iin-- pulses ot such group. A sender diagrammaticallv shown capablel oi'A accomplishing the necessary Vfunctions. and in which the to in the speciiication as produced in the sys-A tem as disclosed are interruptions of the circuit. Obviously this systemmay readily be vadapted to any system in which switches are set in accordance with current 4changes produced at a station., A i,fiirlinstance, to systems in which the setting of the switches is controlled by circuit closures.' 70

' The system herein disclosed is for clearness shown only as a 1000 line system. In such a system there will be live groups of linal selectors, each accessible to200 lines thereof, and the group selectors used will have only lire'of the ten banks thereof utilized, one` bank of contaets'being connected to the trunk lines of the group of linal selectors individual to one group of .200 lines, another connected to another group of final 30 selectors,individual to another 200 lines, and

so on. In accordance with the translating,l

systeindisclosed herein,the selection in the group selector ot the trunk line leading to the group of lines having the proper hundreds digit is such that it' the 100s digit of the desired line is zero or one, the tripping spindle of the group Selector will be, adjusted to release the proper set of brushes. on the brush carriage bythe movement of such spindle one Step or stage. If the s -l digit ot the desired line is two or three,lsuch spindle will be moved threev steps or Stages.

lt' the 100s digit is four or five, the Spindle@ will be moved five steps or Stages. Iftheff l 100s digit is six or seven, such spindle will be moved seven steps or stages, and finally it' the 100s digit is eight or nine, Such Spindle will be moved nine steps or stages. O f coarse. it will be understood that if the sys- 10o tem is tor more than 1000v lines that the in; termelliate steps or stages, that is, second, fourth. sixth. eighth and tenth will be reserved for use when a trunk line is'desired leading to the groups of selectors havingil' if desired,A adjacentlv to each other, so that 1l-5 the first level will he selectedby a single step of the tripping.;` spindle, the second level by three steps of such spindle, the third level by five steps .of such spindle', and so on. Furthermore, if preferred. thelzo arrangement of the lines of thesubscribers upon the final selectors may be so arranged that the trunk line leading; to a correspond inggroup oflOO in each of `the two thousand lines accessible through a group se- 1 26 lector will be selected in the same level of such group selector, such arrangement resulting' in the selection of a line whose 100s digit is zero' in either tlidsndby one step of the tripping spindle ofthe group `selector, lso

itch init() closure 'ekjtabis unent of me t and the eousequent mng simu 'mi-mn uf the steppmg relay L27? thzffovgh the owe winding ad.

1f 2310 wi energized in :saquen sw, 'mth Bosnien, the

. *il a p'laced under the control of the calling subscriber, and the sending circuit from the calling substation is open at the springs 210 bottom and 211 bottom.

The outgoing sequence switch #L50 of the registeringz,r and controlling erpiipincnt, when it wasnmved .troni its iirst position as the incoming,` 4sequence switch A-OO passed throughits-iitth position as above described, continued in motion until it reached. its fourth position. ln passing from its lirst to its second position, a test was made by the spring,r 459 to determine whether the lOOs digit ot' the number registered was odd or even; it'havinp; been vfound tobe odd, the hundreds register is in its seventh position, seven limpulses having been Sent by the calling subscriber operating` his sending mechanism for the digit 3, a circuit was closed for the translating' relay L5-32. lt will be observed that the spring 474 ot.' the 10D-s register isclosed in the following positions; only a fewot' which, vtor clearness, are indicated upon the drawings:

The relay was therefore energized, closing' by its right-hand armature a locking circuit'for itsclt including the springr 455 top, and such relay will be maintained energized until the sequence switch leaves its ninth position.

As the sequence switch 450 passes through its second position the closure and subsequent opening ot' thecircuit ot the power magnet ot the 100s register over the ,spring 458 bottom will drive such register one additional position that in this case into its eighth position. Also as the sequence switch 450 passes through its thirdposition the translating relay lll beiner locked up a oircuit Will be established over the spring,T 46() top, lei't-hand armature oi' such relay and` spring .li-(il bottom, to drive the llltfs register 42 from its eighth into its ninth position.

0n coming into its fourth position the quenco switch (S00 being already in its third position, the fundamental circuit troni the registering and controlling equipment is closed to the group selector shown on Fig. 2. This circuit includes the line relay 242 ot' the group selector, and the selection controllingstepping relay 4533 of said equipment, both ol which relays will be energized. This circuit also includes the springs (312, 473, 457 and (ill bottom. n

The energization of 'the relay drives the sequence switch GOO into its Vfourth Josition over the spring (iii, in which position intensi the circuit for the trip ing spindle power magnet 243 is closctl'ant the tripping,r spindle starts in motion. ln moving Jfrom posi` tion 3 to position 4, sequence switch no() inalies no changes in the Jfundamental foircuit.

)is the relay l was energized coincidentiv with the energizatiou oi the line relay il?, it closed the circuit over the springr '.458 top tor the lower winding ot' the 'loos register i293 the register, therefore, nioved a halt ot' a position, that is, until the closure o ll the circuit through its upper winding' and the positioning spring` il thereof is closed. .\s the tripping spindle ot' the group selector began to move it intermittently closed a circuit to ground` such circuit being so connected to the fundamental circuit that when it closed the'rclay 4.33 will be shunted and deincrgized, though the line relay L is maintained energized. This tlc-energization et' the. relay 4.233 will take place once i'or each movement ot the tripping spint le one step'or stage. y Upon the denergization of the relay 433 the 100s register again moves until it comes into its tenth position, from which position it Will be moved to a position intermediate between its tenth and eleventh positions, when the relay 433 is again energized as the tripping spindle comes into its set position to trip the first set ot' brushes of the group selector; in the continued motion of the tripping spindle -f second dcnergization of the relay 433 takes place and the 100s register is moved into its 11th position, to be moved again into a hosition intermediate between its eleventh and no nu zero positions, when the shunt is again rcuioved at the tripping spindle.

r x i lhe next closure ot the earth connection at the tripping spindle, and the conserpieut third deinergization et' the relay i323 drives the 100s register into its Zero or norinal position. ln this position the spring' l is ile the tripping-spindle power magnet 343' is open at the trout Contact of the line relay 242. and the tripping spindle is brought to rest. Such tripping spindle, having inoved three steps or stages, is now in position to release the third set of brushes on the brushr carriage ol: the Igroupselector, as it willibe recalled that a trunk line leading` to the group ot' final selectors in which the desired line appears is to be found in the third bank or level of such group selector. Y i

As the 10Gs register came into its Zero or normal position, if the incoming sequence switch 400 is in its 9th position-that is, it

or level 'oi' contacts. It will also be recalled that thetens register was set by the subscriber in its `10th position and subsequently moved to its eleventh position. l/Vhen, therefore, the tripping spindle at the final selector moves its first step or stage, the shunting of the relay 433 in the 'Well-knownmanner drives the tens register into its zero or normal position. This movement of the tens register immediately opens the fundamental circuit at the spring 483 of such register, so

that when the shunt circuit through the tripping spindle is opened both the relay 433 and the relay 332 are denergized. At the same time the Aclosing of the spring/482 ofbeing now in position to trip the first set of brushes on the brush carriage, and the sequence switch 300 1s driven from its second lposition to come to rest in its 4th position.

As the. outgoing sequence switch 450 of the registering and controlling equipment moved through its seventh position upon the termination of tens selection the momentary closure of the spring 454 moves the units register one additional position so that when the sequence lswitch stops in eighth position and again closes the fundamental circuit the units registeris in its fourth position.

lThe closure at this timel of ,the fundamental circuit again energizes the relays 332 and433, but this time in the 4th position oi' the sequence switch 300 and the 8th position of thesequencc switch 450. In the 4th position of the sequence -switch 300 the energization of the relay 332 closes a circuit over the spring 306 top from the brush carriage power magnet of the final selector, and such brush carriage begins to move. ln the initial movement oi' the brush carriage, the proper set of brushes (in this case the iirst set) is tripped as the carriage passes the tripping spindle.

ln the subsequent movement of the brush carriage the brushes 334, 335, 336 sweep over -the sets of terminals individual to the lines multiplied to this bank orlerel of contacts. For cach movement of such brushes to a set of terminals the interruptor device closes a circuit to ground from the tunvdamental circuit over thesprings 313 top and 315 in the well-knownmanner, such eircuit to ground as is well understood shuntlocked'up when the sequence switch 450, in

lay 332 energized.

Upon the energization of the relay 433 Aand its subsequent intermittent defnergization due to the shunting action of thecontacts of the interrupter 337 at the iinal selector, the unitsregister will be stepped in the well understood manner, one full position for each energization and subsequent denergization ot' the relay 433. At the vend of eight ot such operations of the relay 433 the units register will again be in its normal position, the selected brushes of the inal selector at this time being about to make contact with the 8th or No. 7 set of contacts of the bank or level to which they are individual. It will berecalled, however, that since the desired line is located in an odd hundred, the particular line desired is to be found in the second half of the final selector, and it is therefore necessary that the selecting loperation should not terminate at i this time. F or this reason the fundamental circuit is not opened at this time at the spring 493 as would be otherwise the case, a shunt being maintained about'such spring, such shunt including the spring 460 bottom,

'left hand armature of'the translating relay 432 and the spring 461 top.

It will be recalled that the relay 432 was passing from its iirst to its second position, tested the condition of the 1005 register 429, and on finding it in a posit-ion corresponding to an odd hundred, comple-ted thecircuit for the translating relay 432'.V The fundamental 100 circuit not being open at this time, the brush carriage at the iinal selector will continue to move'until the units register 431 has made a complete revolution as a result et such' movement. This means that theunits register will take twelve additional steps. It will now be seen i'or what purpose the two additional notches in the interrupter plate of the final selector are provided, as hereinbefore described. To reach the contacts of the desired line after the units register has lirst reached its normal position would otherwise produce only ten denergizations of the stepping relay 433, and', consequently, only ten steps by the units register.

Since it is necessary that the units register should come into its zero or normal positien in order to cause the cessation of selection, it is necessary that two additional steps be provided for'and, consequently, two addi- 120 tional notches are cut in the interrupter plate of the final selector to produce such steps. Therefore, after the steppingr relay 433 has been operated twelve additional times, and as the selected brushes of the final 125 selector are coming into` contact with the 7th set of terminals in the second halt or range of the selected bank or level of the final seiste? comes l' igizntiim, in the in the iinnl which movement in '.i punition ll it ein.

'ing been selected, j and controlrequired for Y iure, as the selth pnsitinn She ne eiicni for the felnjvs niiJ nml l)een suhsiilly established over .envite switch 40() relay; f2-(3 unil inl Lil), flic the Win linge -q'g the ielaj! Silvie?. l 1

:mii clown i (i e ,ii `i alie the piace ef the i i .gh the epi-ing 312 bottom, which in n ien il :is the semence switch 300 leaves iis il s "inn les vlle sequence switch moves om its fen i to its iii-th pm sitirm, ille spring Sil ien opened und botom desee. The relay 331 is mainmined energized, both of its windings now being included in ihe ciicuit and the battery is Connected over he spying Bil bettom t0 the 'pnwei control Test rela"Y i539. At the saine time the spring 307 iop ClGsecl, con- 331 :incl iie spring treiefere energized,

i D i;

nesting' b-i'eiy wih a high resistance Winding of the C et relay 3119. The ifth posiiion of ille sequence switch 300 is the lesting liesimon 'there/ei. lf in his position Tull po entai is found upon the test terminal of the cleifi'ecl line, indicating that the line idle, the "Lest relay 3%) will be eneigized over its righi; hand high insistance Winding. if on ihe other hund the normal potential upon such tesi terminal is reduced by sich line being busy, either as a Calling line or av celled line, will occur in the wellinliziwn n inner. the test relay 3&9 will not u zeil. Assuming iii'st that the line is lmig. such @luy is Consequently energized, closes over its :irmauife :i circuit, through its low iesisnnce left hand Winding :incl the tes?- ifeley 3.259, in parallel to its right, hand winding', -which will so reduce the p0- tentizil 0i' lietest terminal of such seized line that it *will iest busy in all other inl selectors in which it .ippeiu's. Such circuit 'will ulSn energize the rel-1 3v 339 und when the se- :fish 300 @Unies into lie sixth posi- "Spi ingA il? nii he @they over ihe spring 305 zi; lili. and the nefiiiei* Switch l0() te :viering :imi cmielecting operi? is li-ive!! iii-0in Il ii. will mow n iS iiie iimk liney le this botozn, and iie front Contact of relay 35S) und il nach Contact 0i fein); 332, te move it ine iis enih position, in which posiiimi, unil also iii the eleventh position a Circuit will he im nfl clesecl to more ie ini@ vits .'i" lh posiimi.

ie Sixth position of this sequence switch is provided for hunting un idle line to a piivzie li'ixnch exchange, in @use the 'izuiiculsu' line Seiecied is found busy. The :ipp-dmtus ffl' pei'ioi'inim ehi? opentien is not Shmvm hmwvei', und in miler to (l1-ive the se ilumine :swiicii himiglh its siXl positilgn, which i :es Sliviwnj @in idle position, whether the les 'ed line 'found idle or busy, the

Spring Si? is prof led.

'i'he lYel'ih position of the Sequence is the iinjejing position, ln this posiiiiif. ringing; mii-rent is giioieuieil over the (wi-livel liney by the elirSm'eJil" the springs El() bulloni and Sli liotlnm. Y

fw ih'e sequence switch 301') pusezef'lA himigh `iggiili positivi; the immliml lending; tu ci. nied 'by the closure mit the spring 309 bottom. This iis - causesthe' 4momentary energization of the supervisory relay 248, which by the attraction of its armature drives the sequence switch 200 into its eighth position. This would cause thesubscriber -to receive the busy tone by the closure ofthe springs 212 bottom and 213 top, except for the fact that almost immediately after as the sequence switch 300 passes from its eleventh into its twelfth position, the spring 309 bottom is again closed energizing the relay 24S to y drive the sequence switch 200 into its eleventh position. In this .position of the 'se- 'quence switch 200, the springs 212 top and 213 bottom being closed, thesubsc'riber receives the distinctive ringing tone, and willv continue to receive such tone so long as the sequence switch 300 remains in its twelfth position. f

So long as the called subscriber-does not respond, insufficient current will passover the ringing relay 343 to energize it. ,As soon, however, as the path for direct current isV closed at the subscribers substation,

position, the sequence switch 200 being inl its fourteenth position, the sequence switch 600 being in its seventh position, and the sequence switch 300 being in its thirteenth position, the calling subscriber and the called subscriber are now connected, each subscriber-being supplied with transmitter current from'the battery shown in connection `with the repeating coil 239. Conversation may now take place.

'Dz'sconnect/on-Upon the termination of conversation, one or both subscribers return their receivers to their respective switchhooks, thereby opening a circuit over which the supervisory relays 241 and 248 are'maintained energized. Assuming that the called subscriber-first restored his receiver to' its switch hook, the denergization of the relay i 248 closes a circuit over the' springs 203 and 209 bottom, to drive the sequence switch (S00 outv of its seventhposition and into its eighteenth osition. In this movement the sequence switch 600 closed in its 8th position a circuit over the springs 609 and 202top, to drive the sequence switch 200 back to its y normal position. On coming into its 18th position the sequence switch 600 established the usual restoring circuit for the brush carriage ofthe group selector, and such brush carriage moves until the brush 244.- of the interrupter comes in contact with the normal segment, at which time circuit is closed over the spring 61S to energize Ithe relay 237 which stops the movement of the brush car# riage .in the usual manner and drives the sequence switch G00 into its normal position.

As the sequence switch G00 left its 7th position. it opened at the spring ($10 top the circuit of the relay 137 at the first line finder. This relay thereupon, being deiiuergized, drives the. sequence switch 100 from its 5th into its 9th position. positions of this sequence switch a circuit for this relay is again established, provided the calling subscriber has not restored his receiver to its switch hook, which includes the spring108 bottom, the spring 111, the substation circuit and the spring` 112 top. The sequence switch 100 will therefore stop in its 9th position and remain there until the subscriber opens the circuit to direct current at his substation by replacing his receiver upon its switch hook. As soon aS this occurs, the relay 13T will again be deenergzed and drive the sequenceswitch 100 back to its first or normal position. lt will Le observed that the cut-ofi' relay 139 is con- In the Sth and 9th` trolled through the 7th position b v a circuit v including the spring 102 top. and iu the Sth or 9th position by a circuit including the resistance 199 and the spring 110. This transferrof control vis accomplished before the circuit of the cut-oft1 relay 130 was opened at the spring 207.

As the sequence switch .600 left its 7th position, it opened at the springs 605 top and 606 top the circuit for the relay 331 at the final selector. This relay therefore immediately allowed its armatures to retract, its

left-hand armature closing a circuit -over the springs 30S bottom to energize the line,

relay The energization of this relay drives the sequence switch 300 out of its 13th position into its 16th position. On coming into its 16th position, the circuit at the called subscribers substation being al- It will be observed, however, that although the relay 331' at the final'selector is denergized immediately that theA sequence switch 600 leaves its 7th position, itis not again energized by the closure of the spring v610 bottom, as such relay 331 controls Cil tnrough its right-hand armature the energizing current for itselll in all positions, esvcept position l, of the sequence switch BOU. However, in positions o to l? a test guard is maintained on the terminal of the trunk line hy the closure ot' the spring Gl() bottoni.

Assuming that the callinr subscriber firstrestored his receiver to its switch hook, the restoration to normal of the group .selector apparatus, the sequence switch G00, sequence switch .200 and the iirst line finder apparatus, will take place preciselyT as has been hereinhet'ore described, except that these operations are initiated by the deenergization ot' the supervisory relay 2li instead of by the denergization ot' the supervisory relay 2455, as has been described, with the further exception that the sequence switch 100 Wilhnotstop in its 9th position as the circuit for the rela j\v i237 over the calling subscriber-s line will not be established. x

tthe tinal selector,` however` when the sequence switch 300 comes into its 15th and 16th positions the called subscriber not as vet having restored his receiver to its switch hook, a circuit will be established for the relay 332, includingy the springsBOS top. 3l() top, subscribefs line. Sli top and 30S) top. rEl'ieretore, when the sequence switch S00 comes into its 16th position it will there stop and await the restoration of the called suhscribers 'receiver to its switch hook, w iieh, when it occurs, will open the circuit to the rela)Y 332, allowing such relay to deenergize, to drive the sequence switch 300 out of its 16th position, after which the restoration of the final selector apparatus will scribed:

l it/tempted connection. i0 a usg/ Zmc.-It after the final selector switch has-been moved to brine' 'its brushes 5534. 335, -lll into contact f with the terminals ot' the desired line, and the sequence switch E300 is moving'y through its th and 6th positions, such line. should be tonnd busy, insuliicient potential will exist upon the test terminal 342 to accomplish the energization ot' tho relav ,5349, consequently, no energization ot the relay 5139 will take place and when the sequence switch 300 comes into its th position it will stop. and the restoration ot the brush carriage ot the selector will take place over a circuit includingr the arnuil'ure and baci; contact ot the rela)T 339. armature and back contact ot the relayY 33). and spring SOG bottoni.

s the sequence switch B00 passed through its Nth position. it will lie recalled that the closure ot the sprin;l Illfl bottoni caused the energixalion .ol the supervisionY relay 2l*- to drive the sequence switch 2U() into ils Hlli position. ln this position the' bus)v lone is applied to the trunk line and the calling suliscrilnr is thus notilied olt the liusy rondi- Virhen the brash ctor reaches its norwill loe enerffizcd the normal segment et and the vseipienee si .Loh into its lith position. relay being: opened nial po e re z bj.' circuit inc ailing the interrupter Kili, SOO will he driven rhe circuit for sueh at the spring oli-l leaves its 10th position. the sequence sviitch BOO will stop in its 11th position. This sequence switch will reniain in this posit-ion and the sequence switches 600 and 200 will reinain in their 7th and 8th positions respeetivelj,y (the called subscribers line being entirely unatlectedl until the calling snbscriber restores his receiver to its "5h hook when in response to the .flenergif'atioii ot' the supervisorsY reay Q-ll 'the seq swite nl? will be driven from its 8th into its lith position. s it eoines into its 9th position circuit will` be established over the baci: Contact ot' the supervisory relay, and the spring' 209 bottoni. lo drive the sequence switch (lfll out of its ith position. troni which position the restoration of the group selector switch` thesequenee switch (S00. the sequence switch 200 and the apparatus of the i'irst linder will taire' place preciselyv as has beenY iiereinhetore described. Furthermore, the restoration of: the iinal seleetoi` apparatus will also take place as liereinhet'ore lleserioed in'imfdiately that the relaiIv 253i is cleenergize-d as the sequence switch (EGO leaves its rith position.

promofr/re fZ/'wofrzmfc/on.-lt the calling subscriber shouif estore his receiver to its .switch hooi; in the third position'ot the se take place as nas been herelnbefore -ded if (piene-e switch QC. the .delnergization ot the stepping rela;7 will cause the energ'sation ot the changeover relair and the rela v" 2-7 remaining denergized and the rela'v 22H energized, the incoming sequence switch 400 will driven directly7 into its ninth position. from whatever position it may be at the time. When sequence switch lili reach t its ninth posi.'on, the sequence switch will lie di' 'en 'from its hirti into its tr "la position, as has been hereinlwt'ore descriheil. The sequence switch will then be 'further driven into its eleventh position liv the closure of a circuit over the haelt Contact of the supervisor)r relay 241, and from such position the group selector apparatus.. the

ser uence switch (G the se( uence switch No.

as the sequence switch 

